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EQ Orionis
(31 December 2008)

  EQ Orionis is one of the brighter beta Persei-type eclipsing systems (p = 1.746038 days = 2514 minutes = 41.9 hours) of which Algol is the prototype. These are binaries with spherical or slightly ellipsoidal components. It is possible to specify, for their light curves, the moments of the beginning and end of the eclipses. Between eclipses the light remains almost constant or varies insignificantly because of reflection effects, slight ellipsoidality of components, or physical variations. Secondary minima may be absent. An extremely wide range of periods is observed, from 0.2 to >= 10,000 days. Light amplitudes are also quite different and may reach several magnitudes. In the case of EQ Orionis, this amplitude is ~3 magnitudes. This binary is a well-studied one, with numerous references in the literature. The time of primary minimum is predicted by the equation:

HJD = 2452501.4050 + 1.746038 x CycleNo.

Finding chart for EQ Orionis

EQ Ori:
RA(2000) = 04h 57m 22.67s
Dec(2000) = -3° 36' 11.2"

EQ Orionis
(Chart from Starry Night Pro)

Eclipse curves for EQ Orionis

  Observations of EQ Orionis were carried out over several nights for a period of about three hours each night. Each data point represents a 50-second integration exposure using an ST-7XME CCD camera cooled to -30°C and a "Clear" filter. Each point is separated by about one minute. The ten-second difference represents the download and processing time needed before the next exposure begins. The telescope is continuously autoguided. After observing, all of the CCD images in the series are calibrated in the standard way to remove dust donuts and vignetting.

  The figure below shows the eclipse curve for EQ Orionis, along with the five reference stars and three check stars. This is data from 29-30 December 2008 EST (cycle no. 1334), and the observed geocentric time of minimum (middle of eclipse primary minimum) was approximately 30 Dec 2008 03:11:06 UT, or HJD = 2454830.6373. The image on the right is a single CCD frame near the time of mid-eclipse, #134 from a series of 155 images. The positions of EQ Orionis, the five reference stars and the three check stars are indicated in the image and on the graphic. The graphic is generated by MaxIm DL/CCD, using the photometry tool.

EQ Orionis
(Plotted in MaxIm DL/CCD)

Things to Note

  These are preliminary results, based only on inspection of the light curves and corresponding CCD images. The equations used to generate heliocentric predictions for primary minimum were corrected to get a geocentric UT time for the predicted minima. The observed geocentric UT time of primary minimum is determined from the light curve, and corrected again to determine the observed heliocentric Julian date of mid-eclipse.

  The magnitudes shown on the graphics are instrumental magnitudes, and they have not been transformed to a standard photometric system. Nevertheless, the "constant" values for the magnitudes of the reference and check stars demonstrate that the telescope-CCD system and evening conditions were stable.

  This deep light curve is typical of Algol-type eclipsing binaries. More observations will be added.

  All available data are shown in the figure below. The primary eclipse is occuring about 20 minutes later than predicted.

EQ Orionis eclipse cycle
          EQ Orionis - phase vs delta magnitude (Ref1 - EQ Ori)


  ●  SIMBAD basic data

  ●  SIMBAD clickable finding chart

  ●  Aladin preview image

  ●  Reference Literature

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This data and information on this page are Copyright © 2008-2009, Richard A. Berg, Washington, DC